Additional CU

[morqthana]

Main earth terminal.

Should be G/Y.

Phenolics are brittle and are easily broken both by those installing them and by the usual junk that people insist on storing next to electrical equipment.
They also absorb moisture and become conductive, and when both L&N are in the same moulding, carbon tracks can form between them which eventually leads to breakdown and fire.

Sorry - I thought it was the 2-pole aspect you didn't like, not the Bakelite.

 

[JohnW2]

That’s a surprise to me . I assumed any CU is.

That presumably is what the 'author' intended, but he/she did not think carefully enough in their choice of words, since, per the words they chose to use) the only work which is notifiable is replacement of a CU, not installing an additional one.

However, they may have 'got away' with that oversight ('more by luck than judgement'!) - since installation of an additional CU presumably will presumably always involve the creation of 'new circuits' - which is notifiable!

Kind Regards, John

 

[morqthana]

If an existing MCB in an existing CU needs to be replaced, is that a new circuit?

 

[JohnW2]

If an existing MCB in an existing CU needs to be replaced, is that a new circuit?

I wouldn't say so. BS7671 defines a circuit as everything supplied by A common OPD, not "a particular" common OPD - so if what is connected to the replacement MCB is the same as what was connected to the previous one, I wouldn't say that a 'new circuit' has been created.

Of course, once the MCB has been replaced, one is then free to alter/extend the ('existing') circuit as much as one wants without any requirement for notification

 

[SUNRAY]

Of course, once the MCB has been replaced, one is then free to alter/extend the ('existing') circuit as much as one wants without any requirement for notification

I had exactly that arguement when my daughter moved house following divorce and her ex created so much hassle I had to get the alterations 'certified'.
There was a 32A circuit for a hot tub on 7/0.044", when they moved in it fed only a DSSO in the conservatory from the original isolator (actually a cooker switch with socket), also in the conservatory and it didn't work due to faulty MCB. I replaced it with a 45A as a get it going temp to run their fridge and freezer which didn't fit in the kitchen.
The intentions: Create a WC in the office space, repurpose the existing downstairs toilet space (to house the fridge and freezer) which was off the utility room (more like a passage) which was off the kitchen (and a very inconvenient place for a convenience, particularly for elderly grandparents with walking aids).

They moved from a house with on-suite shower & WC + on-suite shower + family bathroom + downstairs WC to no on-suite. Reality soon kicked in so the plans changed to: Create a full shower room in the office space, rather than just a WC. That was done as a matter of urgency.

Then the lounge massive brick fireplace and extension for large CRT TV to stand on removed to make provision for the obligatory huge TV, this required alterations to the ring circuit so included a couple of sockets in the conservatory (making the hot tub circuit redundant and chopped off).

Next the original WC decommisioned and the wall removed to extend the utility passage to to house the fridge and freezer, washing machine, tumble drier and a number of kitchen cupboards, worktop etc which meant significant changes to that ring cuircuit.

Returning to the shower the decision was made to add an electric heater as it was a very long pipe run from the combie and took ages to get hot, the original hot tub cable was again chopped and diverted (now only a 3-4m run rather than the original >15m) I even used the original cooker switch for the isolator.

So the only time I needed to go into the CU was to change the faulty MCB and technically the electrical work was all alterations. For some reason I didn't get, her ex seemed to mouth off about the changes to the estate agent and how I'd done the work.They of course then wanted the paperwork and the easiest thing to get done was a PIR (EICR).

Ironically the only part that really needed paperwork was the plumbing which was completely missed.

 

[ebee]

I had exactly that arguement when my daughter moved house following divorce and her ex created so much hassle I had to get the alterations 'certified'.
There was a 32A circuit for a hot tub on 7/0.044", when they moved in it fed only a DSSO in the conservatory from the original isolator (actually a cooker switch with socket), also in the conservatory and it didn't work due to faulty MCB. I replaced it with a 45A as a get it going temp to run their fridge and freezer which didn't fit in the kitchen.
The intentions: Create a WC in the office space, repurpose the existing downstairs toilet space (to house the fridge and freezer) which was off the utility room (more like a passage) which was off the kitchen (and a very inconvenient place for a convenience, particularly for elderly grandparents with walking aids).

They moved from a house with on-suite shower & WC + on-suite shower + family bathroom + downstairs WC to no on-suite. Reality soon kicked in so the plans changed to: Create a full shower room in the office space, rather than just a WC. That was done as a matter of urgency.

Then the lounge massive brick fireplace and extension for large CRT TV to stand on removed to make provision for the obligatory huge TV, this required alterations to the ring circuit so included a couple of sockets in the conservatory (making the hot tub circuit redundant and chopped off).

Next the original WC decommisioned and the wall removed to extend the utility passage to to house the fridge and freezer, washing machine, tumble drier and a number of kitchen cupboards, worktop etc which meant significant changes to that ring cuircuit.

Returning to the shower the decision was made to add an electric heater as it was a very long pipe run from the combie and took ages to get hot, the original hot tub cable was again chopped and diverted (now only a 3-4m run rather than the original >15m) I even used the original cooker switch for the isolator.

So the only time I needed to go into the CU was to change the faulty MCB and technically the electrical work was all alterations. For some reason I didn't get, her ex seemed to mouth off about the changes to the estate agent and how I'd done the work.They of course then wanted the paperwork and the easiest thing to get done was a PIR (EICR).

Ironically the only part that really needed paperwork was the plumbing which was completely missed.

Life is full of those little ironies my friend

 

[morqthana]

I wouldn't say so. BS7671 defines a circuit as everything supplied by A common OPD, not "a particular" common OPD - so if what is connected to the replacement MCB is the same as what was connected to the previous one, I wouldn't say that a 'new circuit' has been created.

So if a new MCB in an existing CU doesn't create a new circuit, what if there were 2 CUs and the cable(s) were moved from one CU to the other one?

You can probably see where I'm going with this.

It's easy to joke about the ship of Theseus/Trigger's broom, but if a "new circuit" requires everything to be new, and installing a CU with no final circuits isn't notifiable...

 

[ebee]

What about a MCB existing and being replaced by an MCB of different rating , does this qualify or not qualify as a new circuit? Ask ten electricians and you will get eleven differing answers I think.

Mind you I can easily envisage both of you constructing a set of logical steps to comply and/or not comply with reasoning of others in order to prove/disprove their argument and you could also conspire to work together or against each other equally as well.

I used to have a gaffer like that, he would argue with what someone said and “prove” them wrong then the next person comes along and says the opposite and he would prove them wrong as well and justify the first person as being correct. He lived to argue about everything everybody said . He was BRILL

 

[Murdochcat]

What about a MCB existing and being replaced by an MCB of different rating , does this qualify or not qualify as a new circuit?

Definitely not a new circuit

 

[JohnW2]

So if a new MCB in an existing CU doesn't create a new circuit, what if there were 2 CUs and the cable(s) were moved from one CU to the other one? .... You can probably see where I'm going with this.

Yes I can -and I suppose the answer depends on the extent to which one is going to allow common sense to prevail.

To my mind, common sense says that if 'some wiring' is moved from one OPD to another with the same In (or, I suppose, a lower In) that no 'new circuit' has been created - and that remains true regardless of whether it is moved to an OPD in the same or a different enclosure.

More generally, I would think that a 'new circuit' refers to a circuit ('some wiring') that did not previously exist - which, in turn (given BS7671 definition of a circuit) implies that it is connected to an OPD that did not previously exist (or, at least, an OPD that previously had nothing connected to it). However ...

What about a MCB existing and being replaced by an MCB of different rating , does this qualify or not qualify as a new circuit? Ask ten electricians and you will get eleven differing answers I think.

That is, indeed, the one situation where there is scope for debate, and for differing opinions/views. Given that the requirement for notification (or a 'new circuit') presumably relates to perceived 'safety issues', it is fairly easy to argue that replacing an MCB with one with a 'higher rating' (In) raises potential 'safety concerns' and therefore should be considered a 'new circuit'.

Even more generally, some might express a view that any 'repurposing' of a circuit rendered it a new circuit' that required notification. However, provided only that the OPD remained unchanged (and appropriate for the wiring), I don't really see that as an issue - even if some idiot 'repurposed' a 6A lighting circuit to feed a shower, the cable would still be adequately protected by the 6A OPD and the worst that would happen would be for the shower to cause the OPD to operate.

It's easy to joke about the ship of Theseus/Trigger's broom, but if a "new circuit" requires everything to be new, and installing a CU with no final circuits isn't notifiable...

As I think we've discussed in the past, the view I've expressed above does open up the possibility of what would seem to be a potential 'loophole'. .... install an 'additional' (not 'replacement'!) CU adjacent to the existing one, the new CU having a set of OPDs with the same ratings as those in the original CU. If you were to accept what I've suggested above, then I could (without a requirement to notify) transfer the final circuits, one at a time, from old CU to the new one (with identically rated OPDs) - eventually getting to the stage at which all final circuits had been transferred. The 'additional' CU would then be serving all final circuits and the old one would be serving nothing (and I see nothing which suggests that removal of an 'unused' CU is notifiable)

 

[ebee]

Gosh. And some thought that merely defining intelligence in AI could be a tricky concept!

Makes the logistics of justifying a complete change of consumer unit and circuits from what existed to what is now in a set of predefined stages completely change from additions to renewals at the stroke of a pen in order to satisfy a number logic or rule or law. We then achieve a state whereby we can achieve owt with nowt (almost) and everyone is happy.

Makes the age old saying “ We did it by ways and means” come into common usage

 

[JohnW2]

Gosh. And some thought that merely defining intelligence in AI could be a tricky concept! .... Makes the logistics of justifying a complete change of consumer unit and circuits from what existed to what is now in a set of predefined stages completely change from additions to renewals at the stroke of a pen in order to satisfy a number logic or rule or law. We then achieve a state whereby we can achieve owt with nowt (almost) and everyone is happy.

I imagine that we all understand roughly 'what was intended', the problem being that the wording of the notification rules in the legislation is inadequate and certainly not properly 'thought through'.

A good lawyer friend of mine recently retired after decades of working for government (governments) in drafting legislation. Throughout her working life, she was very conscientious and fastidious in her attempts to make legislation 'as clear and unambiguous' as it could possibly be, and I feel sure that she would be far from impressed by what we are talking about!

Having said that, in this case I don't think that much 'blame' can be attributed to the lawyers and bureaucrats, since they will necessarily have had to be guided by 'expert (electrical) advice' and hence may well have been led to believe that "replacing a CU" and "installing a new circuit" were both adequately clear (and comprehensive/exhaustive) to achieve what was required. However, some 'field testing' may well have revealed at least some of the problems with the wording that has been used.

Kind Regards, John